1. Field of the Invention
This invention relates to silicone coating materials for optical communication glass fibers. More precisely, this invention concerns silicone coating materials 2 for optical communication glass fibers which have a cross-sectional structure in which a glass fiber 1 core is covered with a silicone coating material 2 and the exterior of the silicone coating material is covered with a thermoplastic resin coating material 3.
2. Description of the Prior Art
Optical communication glass fibers are currently being used in many communication systems such as public communications, in-house communications, computer datalinks and cable television because they are light weight and exhibit large transmission capacities, long-distance transmission abilities and electric insulation properties. The glass fibers which are normally used for optical communications are very fine fibers with a diameter of approximately 100 microns. Because the strength is significantly reduced and the transmission characteristics are impaired when the surface is contaminated, the surface is generally protected with a plastic or metal film. In addition, the transmission characteristics of optical communication glass fibers are significantly impaired when the fibers are slightly bent (microbending loss). Therefore, optical communication glass fibers are normally coated with a resin with a relatively low Young's modulus such as a silicone resin, urethane resin, ethylene-vinyl acetate resin, or epoxy acrylate resin as the primary coat and then with a resin with a relatively high Young's modulus such as nylon, polyethylene, or poly(vinyl chloride) as the secondary coat.
Fusion connection or butt connection is applicable for the connection of optical communication glass fibers. In both cases, it is readily understood that connection is preferably carried out after the primary and secondary coats have been completely removed. In particular for fusion connection, residual coating material is burned during the fusion operation and the combusted material enters the glass in the fused section which causes a significant decline in strength.
Because silicone primary coating materials exhibit an excellent adhesiveness for glass and a low Young's modulus, they have been widely utilized. In contrast, they are difficult to remove in the connection operation, i.e., the peelability is poor. Thus, it is a drawback that the silicone adhered on the glass fiber surface is not easily removed. This drawback is amplified by the further increase in adhesion when the thermoplastic resin is coated over the silicone coating material.
An object of this invention is a silicone coating material which does not suffer the drawbacks of conventional silicone coating materials, i.e., they have an excellent peelability, while retaining the merits of the conventional silicone coating materials.